Microwave frequencies are commonly used for the transmission of data and telecommunications in both ground-based and space-based systems, as well as other uses. Microwave systems include the use of a transmitter, an antenna to radiate the microwave signal, and a receiver. The transmitter generates a transmission wave of a particular frequency and outputs a narrow beam at microwave frequencies from the antenna, which is then intercepted by the receiver.
While telecommunications and other microwave signal uses have most commonly employed the use of microwave frequencies of from 1 gigahertz (GHz) to 30 GHz, technology improvements may allow for the use higher frequency waves, for example, at 44 GHz, 77 GHz, 94 GHz, and higher. However, to enable these higher frequency microwave signals, transmitter and receiver hardware must be formed to more strict design tolerances.
Microwave circuitry for use in telecommunications is typically formed as a multilayered printed circuit board (PCB) using conventional PCB fabrication techniques. The PCB's may be up to several feet in width, a perimeter of over 100 inches, and have an area of several hundred square inches (in2), or over 1,000 in2. Each microwave circuit substructure, for example, one or more filters, resonators, inductors, etc., is formed using conductive lines (e.g., conductive interconnects) on the PCB and discrete components such as capacitors, diodes, relays, etc., attached to the PCB using a conductor such as solder or a conductive paste. The conductive lines may be formed from a metal layer that is chemically etched using an acid.
While wafer microfabrication techniques using, for example, photolithographic processes can form circuitry having the required dimensions and tolerances, device sizes are limited by present technology to maximum wafer dimensions. For example, while silicon semiconductor wafers presently have a maximum diameter of about 300 millimeters (mm), microwave PCB's may have a required size of several feet in width. Further, contract manufacturers may be limited to less than maximum wafer sizes, for example, to 125 mm wafers. Additionally, wafer fabrication is expensive and requires costly manufacturing equipment and cleanroom environments.